The present invention relates to medical instrumentation; and more particularly to iontophoretic catheter apparatus and application for the sterilization of a fluid path.
It has been estimated that approximately ten to fifteen percent of hospitalized patients are subject to indwelling urinary catheterization. Of these catheterized patients, about twenty-five percent contract bacterial infections of the urinary tract.
The insertion of a catheter through the urethra into the bladder often contaminates the normally sterile internal duct environment. As a catheter is introduced through the urethra passageway or a surgically created opening to the bladder, bacteria normally found on the skin surface are introduced onto the catheter surfaces. As the catheter progresses through the urethra or opening, a bacterial inoculum is carried along to the normally sterile sites. The bacteria then colonize and eventually spread to regions uncontacted by the catheter.
Accordingly, it is recognized by physicians that catheterization presents a risk of bacterial induced cystitis or pyelonephritis and that risk increases proportionally with the period of catheterization time.
Various methods and treatments have been employed in an effort to reduce the possibility of bacterial infection associated with catheterization. Most commonly, physicians have sought to avoid infection by limiting the time of catheterization, by increasing water intake to increase voiding, by designing catheter systems closed to external contaminants, by preventing urine from flowing retrograde into the bladder, and by frequently exchanging used catheters for new ones. Further, antibiotics have been applied both prophylactically and remedially to reduce the occurrence of bacterial infection associated with catheterization.
Specifically, topical antibiotics such as neomycin, bacitracin, and polymyxin B sulfate are applied to the catheter surfaces prior to catheter insertion. The intent of this treatment is to prevent subsequent infection by the bacteria initially carried along the catheter surface as it progresses through the urethra. Although such antibiotic treatment is often effective in preventing initial contamination, if the catheter remains in place for an extended period of time systemic reapplication of the antibiotic is necessary to maintain prophylaxis.
Recently it has been suggested that silver plated catheters help prevent urinary tract infections through a process called oligodynamics. Heavy metals, in particular, gold, silver and copper, exert in the form of metal ions a profound bacterial effect, the so-called oligodynamic activity. Such material is effective in very small quantities and effective over long periods of time to inhibit the growth of bacteria. For example, U.S. Pat. No. 4,054,139 describes an oligodynamic catheter which comprises an internal and external immobile surface coating of silver onto a catheter. According to the invention, small quantities of silver exposed as part of the catheter surface are effective in avoiding infection of surrounding tissues contacting the catheter surface. Because of the limited diffusion of silver ions from the silver coating, the antibacterial effect, however, is primarily a site-specific surface effect.
Although some of the prior art solutions have been successful under certain conditions, the need remains for other practical and inexpensive solutions to the problem of catheterization associated bacterial infection. Especially, the need remains for a catheter device which is effective in killing bacteria suspended in a fluid phase over an extended period of time.